The present invention relates to ink compositions for ink-jet printing, and more particularly, to ink compositions that comprise organo-phosphonic acids and their salts.
The ink-jet printing process involves the ejection of fine droplets of ink onto a print medium such as paper in response to electrical signals generated by a microprocessor. Typically, an ink-jet printer utilizes a pen set mounted on a carriage that is moved relative to the surface of a print medium. In commercially available ink-jet color printers, such as the DESKJET(trademark) printer available from Hewlett-Packard Company. A typical pen includes print heads with orifice plates that have very small nozzles (10-50 xcexcm diameter) through which the ink droplets are ejected. Adjacent to these nozzles are ink chambers where ink is stored prior to ejection. Ink drop ejection is currently achieved either thermally or piezoelectrically. In thermal ink-jet printing, each nozzle is associated with a resistor element. Each resistor element is in turn connected to a microprocessor, whose signals direct one or more resistor elements to heat up rapidly. This causes a rapid expansion of ink vapor that forces a drop of ink through the associated nozzle onto the print medium. A variety of complex interactions between the ink and pen structure (e.g. the resistor element, nozzle etc.) are known to affect both the short and long term reliability of pen performance and hence of print quality. Examples of these interactions include corrosion due to presence of metal ion impurities or other reactive components in the ink composition; kogation, defined as the build up of residue on the surface of resistor elements; puddling, defined as the formation of ink puddles on the orifice plates of the print head; and crusting, defined as the formation of insoluble crusts on the orifice plates of the print head.
High dot gain inks are desirable for ink jet printing because they give a large dot size for a given drop volume. The major advantage is that lower drop volumes can be used for a given printing application, resulting in lower cost per copy, reduced plain paper cockle and reduced amount of ink on transparency film. Most high dot gain inks have low surface tension, which causes the ink to spread across the orifice plates of the print head, to form so-called xe2x80x9cpuddling.xe2x80x9d The ink drops must fire through the puddles, which results in misdirected drops and streaking of images, and lowers print head reliability and results in poor print quality.
Several methods of addressing the puddling are known in the art, for example, use of surfactants to adjust the ink property (U.S. Pat. No. 5,656,655), improved orifice plate designs (U.S. Pat. Nos. 5,595,785 and 5,434,606), improved designs of ink channel geometry (U.S. Pat. Nos. 5,755,032 and 5,274,400), and lastly, a more effective wiping system (U.S. Pat. No. 5,786,830) to clean the puddles. In some instances, adding surfactants is not an option because of adverse effect of the surfactants on the print quality. Mechanical wiping and design changes are often inefficient and add considerable expense to the cost of the printer.
Accordingly, a need exists in the art for a means to produce ink compositions for ink-jet printers that control puddling and yet exhibit favorable interactions with the components of the pen structure and in particular with the intented print media (e.g. paper) to maintain large dot size and high image quality.
The invention is an ink-jet ink composition. The composition comprises at least one colorant and a vehicle. The vehicle includes at least one organo-phosphonic acid or sodium or potassium salt of the said acid (In the following text, when organo-phosphonic acid is cited, the acid and it salt are implied). The vehicle may contain mixtures of two or more organo-phosphonic acids. The organo-phosphonic acid may be monofunctional or polyfunctional. Preferably the organo-phosphonic acid is polyfunctional. The concentration of organo-phosphonic acid may be from about 0.05 to about 10 wt %. The organo-phosphonic acids may be of general formula 
wherein R1 and R2 are phosphonic acid groups, and R3 and R4 can each, independently of each other, be hydrogen, a hydroxyl group, a phosphonic acid group, an alkyl group, an aryl group, or a substituted alkyl or aryl group having substituents selected from the group of alkyl groups, aryl groups, hydroxyl groups, phosphonic acid groups, ether groups, ester groups, and mixtures thereof. Preferably R2 is a phosphonic acid group. More preferably R2 is a phosphonic acid group, R3 is a methyl group, R4 is a hydroxyl group and the organo-phosphonic acid is hydroxyethylene di(phosphonic acid) (HEDP).
The organo-phosphonic acids may be of general formula 
wherein R1 is a methylene phosphonic acid group, and R2 and R3 can each, independently of each other, be hydrogen, a hydroxyl group, an alkyl group, an aryl group, or a substituted alkyl or aryl group having substituents selected from the group of alkyl groups, aryl groups, hydroxyl groups, phosphonic acid groups, ether groups, ester groups, and mixtures thereof. Preferably R2 is a methylene phosphonic acid group. More preferably R2 and R3 are methylene phosphonic acid groups and the organo-phosphonic acid is amino tri(methylene phosphonic acid) (ATMP).
The organo-phosphonic acids may be of general formula 
wherein n is an integer between 1 and 6, R1 is a methylene phosphonic acid group, and R2, R3 and R4 can each, independently of each other, be hydrogen, a hydroxyl group, an alkyl group, an aryl group, or a substituted alkyl or aryl group having substituents selected from the group of alkyl groups, aryl groups, hydroxyl groups, phosphonic acid groups, ether groups, ester groups, and mixtures thereof. Preferably R2, R3 and R4 are methylene phosphonic acid groups. Preferably n=2 and the organo-phosphonic acid is ethylene diamine tetra(methylene phosphonic acid) (EDTMP), or n=6 and the organo-phosphonic acid is hexamethylene diamine tetra(methylene phosphonic acid) (HDTMP).
The organo-phosphonic acids may be of general formula 
wherein n is an integer between 1 and 6, R1 is a methylene phosphonic acid group, and R2, R3, R4 and R5 can each, independently of each other, be hydrogen, a hydroxyl group, an alkyl group, an aryl group, or a substituted alkyl or aryl group having substituents selected from the group of alkyl groups, aryl groups, hydroxyl groups, phosphonic acid groups, ether groups, ester groups, and mixtures thereof. Preferably R2, R3, R4 and R5 are methylene phosphonic acid groups. Preferably n=2, and the organo-phosphonic acid is diethylene triamine penta(methylene phosphonic acid) (DTPMP).
The vehicle may further include from about 0 to about 10 wt % surfactants, and from about 0.1 to about 40 wt % organic cosolvents. The pH of the ink composition may be from about 2 to about 10.
The invention will now be described with particular reference to certain preferred embodiments of the ink-jet ink compositions of the invention.
Exemplary embodiments of the ink compositions comprise, by weight (all percentages are by weight unless otherwise indicated) from 0.1 to 40%, preferably from 5 to 25% organic cosolvent; from 0 to 10%, preferably from 0.1 to 5% surfactant; from 0.5 to 10%, preferably from 0.5 to 5% colorant; and from 0.05 to 20%, preferably from 0.1 to 10%, organo-phosphonic acid. The remainder of the ink compositions are mostly water; however, other components including biocides that inhibit growth of microorganisms such as the preservative PROXEL(trademark) GXL (available from Avecia Incorporated); chelating agents such as EDTA that eliminate deleterious effects of heavy metal impurities; buffers; and viscosity modifiers, may be added to improve various properties of the ink composition.
Organic Cosolvents
One or more organic cosolvents may be used to prepare the ink compositions of the present invention. In a preferred embodiment, the organic cosolvents are water-soluble. Many of the water soluble organic cosolvents known for use in ink-jet printing may be employed in the practice of this invention. For the purposes of clarification only, and not for limitation, some exemplary water-soluble organic cosolvents suitable for this purpose are set forth below.
Exemplary water-soluble organic cosolvents include, but are not limited to, aliphatic alcohols, aromatic alcohols, diols, triols, amides, ketones, polyketones or ketoalcohols, nitrogen-containing heterocyclic ketones, ethers, glycol ethers, polyglycol ethers, alkylene glycols, polyalkylene glycols, thioglycols containing alkylene groups, lower alkyl ethers of polyhydric alcohols and lactams.
The concentration of the organic cosolvents may range from 0.1 to 40 wt %, preferably from 5 to 25 wt %.
Surfactants
One or more water-soluble surfactants may be employed in the formulation of a vehicle for the ink. Many of the water-soluble surfactants known for use in ink-jet printing may be employed in the practice of this invention. For the purposes of clarification only, and not for limitation, some exemplary water-soluble surfactants suitable for this purpose are set forth below.
For convenience, examples of surfactants are divided into two categories: (1) non-ionic and amphoteric and (2) ionic. The former class includes the TERGITOL(trademark) and BRIJ(trademark) families of alkyl polyethylene oxides (POEs), available from Union Carbide Corporation and the ICI Group, respectively; certain members of the ZONYL(trademark) family of fluorosurfactants, available from DuPont Corporation; the FLUORAD(trademark) family of fluorinated alkyl esters available from 3M Company; the TRITON(trademark) family of alkyl phenyl POEs available from Union Carbide Corporation; the PLURONIC(trademark) family of ethylene oxide/propylene oxide block copolymers available from BASF Corporation; the SURFYNOL(trademark) family of acetylenic POEs available from Air Products Incorporated; POE esters; POE diesters; POE amines; and POE amides. U.S. Pat. No. 5,106,416 (incorporated by reference herein) discusses many of the surfactants listed above in greater detail. Amphoteric surfactants such as substituted amine oxides or members of the MACKAM(trademark) family of octylamine choloroacetic adducts available from the McIntyre Group are also useful in the practice of this invention. Cationic surfactants such as protonated POE amines, and anionic surfactants such as members of the DOWFAX(trademark) family of diphenyl sulfonate derivatives available from the Dow Chemical Company, and the CRODAFOS(trademark) family of ethoxylated oleoalcohol phosphate esters available from Croda Incorporated, may also be used.
The ink composition of the present invention comprises by weight from 0 to 10%, preferably from 0 to 5%, surfactant.
Colorants
One or more colorants may be employed in the ink composition, typically dyes or pigments. The dye or pigments may be non-ionic, cationic, anionic, or mixtures thereof. Any of the color dyes or pigments known for use in ink-jet printing may be employed in the practice of this invention. For the purposes of clarification only, and not for limitation, some exemplary colorants suitable for this purpose are set forth below.
Suitable colorants for the present invention include but are not limited to aqueous dyes such as Reactive Red 180, Direct Blue 86, Direct Blue 199, Direct Yellow 132, Acid Yellow 132, Direct Red 9, Direct Red 32, Acid Yellow 23, Acid Blue 185, Acid Blue 9, Acid Red 17, Acid Red 52, and Acid Red 249.
Suitable colorants for the present invention include but are not limited to pigments such as the PALIOGEN(trademark) and HELIOGEN(trademark) pigment families available from BASF Corporation; the CHROMOPHTAL(trademark) and MONASTRAL(trademark) pigment families available from Ciba Specialty Chemicals Corporation; the TI-PURE(trademark) family of titanium dioxide pigments available from DuPont Corporation; the MONARCH(trademark) pigment family from Cabot Corporation; and the NOVOPERM(trademark), HANSA(trademark) and HOSTAPERM(trademark) pigment families available from Clariant Corporation.
The ink composition of the present invention comprises by weight from 0.5 to 10%, preferably from 0.5 to 5% colorant.
Organo-Phosphonic Acids
One or more organo-phosphonic acids may be included in the ink composition of the present invention. The organo-phosphonic acid may be monofunctional or polyfunctional. Preferably the organo-phosphonic acid is polyfunctional. Examples of suitable organo-phosphonic acids include organo-phosphonic acids of general formula 
wherein R1 and R2 are phosphonic acid groups, and R3 and R4 can each, independently of each other, be hydrogen, a hydroxyl group, a phosphonic acid group, an alkyl group, an aryl group, or a substituted alkyl or aryl group having substituents selected from the group of alkyl groups, aryl groups, hydroxyl groups, phosphonic acid groups, ether groups, ester groups, and mixtures thereof. In one embodiment, R2 is a phosphonic acid group. In a preferred embodiment, R2 is a phosphonic acid group, R3 is a methyl group, R4 is a hydroxyl group and the organo-phosphonic acid is hydroxyethylene di(phosphonic acid) (HEDP, available as DEQUEST(trademark) 2010 from Solutia Incorporated or as BRIQUEST(trademark) ADPA-60AW from Albright and Wilson Americas Incorporated).
Other examples of organo-phosphonic acids that may be used according to the present invention include organo-phosphonic acids of general formula 
wherein R1 is a methylene phosphonic acid group, and R2 and R3 can each, independently of each other, be hydrogen, a hydroxyl group, an alkyl group, an aryl group, or a substituted alkyl or aryl group having substituents selected from the group of alkyl groups, aryl groups, hydroxyl groups, phosphonic acid groups, ether groups, ester groups, and mixtures thereof. In one embodiment, R2 is a methylene phosphonic acid group. In a preferred embodiment, R2 and R3 are methylene phosphonic acid groups and the organo-phosphonic acid is amino tri(methylene phosphonic acid) (ATMP, available as DEQUEST(trademark) 2000LC from Solutia Incorporated or as BRIQUEST(trademark) 301-50A from Albright and Wilson Americas Incorporated).
Yet other examples of organo-phosphonic acids that may be used according to the present invention include organo-phosphonic acids of general formula 
wherein n is an integer between 1 and 6, R1 is a methylene phosphonic acid group, and R2, R3 and R4 can each, independently of each other, be hydrogen, a hydroxyl group, an alkyl group, an aryl group, or a substituted alkyl or aryl group having substituents selected from the group of alkyl groups, aryl groups, hydroxyl groups, phosphonic acid groups, ether groups, ester groups, and mixtures thereof. In one embodiment, R2 is a methylene phosphonic acid group. In another embodiment, R2 and R3 are methylene phosphonic acid groups. In yet another embodiment, R2, R3 and R4 are methylene phosphonic acid groups. In yet another preferred embodiment, n=6 and the organo-phosphonic acid is hexamethylene diamine tetra(methylene phosphonic acid) (HDTMP, available as DEQUEST(trademark) 2054 from Solutia Incorporated, or as BRIQUEST(trademark) 462-23 from Albright and Wilson Americas Incorporated).
Yet other examples of organo-phosphonic acids that may be used according to the present invention include organo-phosphonic acids of general formula 
wherein n is an integer between 1 and 6, R1 is a methylene phosphonic acid group, and R2, R3, R4 and R5 can each, independently of each other, be hydrogen, a hydroxyl group, an alkyl group, an aryl group, or a substituted alkyl or aryl group having substituents selected from the group of alkyl groups, aryl groups, hydroxyl groups, phosphonic acid groups, ether groups, ester groups, and mixtures thereof. In one embodiment, R2 is a methylene phosphonic acid group. In another embodiment, R2 and R3 are methylene phosphonic acid groups. In yet another embodiment, R2, R3 and R4 are methylene phosphonic acid groups. In yet another embodiment, R2, R3, R4 and R5 are methylene phosphonic acid groups. In a preferred embodiment, n=2 and the organo-phosphonic acid is diethylene triamine penta(methylene phosphonic acid) (DTPMP, available as DEQUEST(trademark) 2060S from Solutia Incorporated or as BRIQUEST(trademark) 543-45AS from Albright and Wilson Americas Incorporated). The ink composition of the present invention comprises by weight from 0.1 to 20%, preferably from 0.5 to 10%, 2 to 10%, or 5 to 10% organo-phosphonic acid.